1. Field of the Invention
The present invention is directed to an annular or internal-diameter saw for cutting off wafers from a workpiece, comprising a saw blade which is clamped via a clamping edge of a clamping edge ring. In addition, the present invention is also directed to a method of protecting the clamping edge and of cleaning the saw blade of an annular or internal-diameter saw during the cutting off of wafers from a workpiece.
2. The Prior Art
EP-464 668 A1 describes the basic construction, the mode of operation and a common field of use of annular or internal-diameter saws.
During the cutting off of wafers from a workpiece by means of an annular or internal-diameter saw, a wafer or wafer residues may be thrown radially against the clamping edge of the saw blade clamping system. This results in high wear of the clamping edge. In addition, wafers to be cut off subsequently may be damaged or destroyed by a wafer or wafer residues adhering to the saw blade.
It is therefore advantageous to keep that side of the saw blade on which a wafer is obtained during the cutting off operation free from a wafer or wafer residues. Thus the liquid jet of a cleaning agent may be moved radially back and forth over the side of the saw blade when the saw blade is rotating. If this is not successful, the saw blade, outside the field of view of the operator, may be cleaned. For example, the cleaning may be done with a brush having a long handle, by the brush hairs being pressed against the saw blade at the same time as the flushing with water is occurring. In this case, however, wafers or wafer residues, called workpiece residues below, may be drawn onto the saw blade by a water film. The adhesion forces may be so strong that the saw spindle has to be switched off and the workpiece residues have to be removed by hand.
An undamaged clamping edge is necessary for optimum clamping of the saw blade and for retaining the clamping of the saw blade during the cutting off of wafers. It is also necessary for keeping undesirable axial deflection movements of the saw blade, which are directed perpendicularly to the cutting direction, as small as possible.
It is an object of the present invention to avoid awkward handling methods for cleaning the saw blade and at the same time to provide improved protection of the clamping edge from workpiece residues which have been thrown off.
The present invention provides a component of an annular or internal-diameter saw for cutting off wafers from a workpiece, comprising a saw blade which is clamped via a clamping edge of a clamping edge ring, the annular or internal-diameter saw having an element which partly screens the clamping edge and is arranged in the vicinity of the clamping edge and the saw blade, and an outer material layer on the clamping edge, the outer material layer facing the element and being designed to be substantially harder than a clamping edge material located behind it.
The present invention is also directed to a method of protecting the clamping edge and of cleaning the saw blade of an annular or internal-diameter saw during the cutting off of wafers from a workpiece, wherein workpiece residues thrown against the clamping edge are shattered when striking the clamping edge by virtue of the fact that an element partly screening the clamping edge is provided in the vicinity of the clamping edge and the saw blade, and the clamping edge is given high strength by virtue of the fact that an outer material layer on the clamping edge facing the element is produced from a material which is substantially harder than a clamping edge material located behind it.